The invention relates to ball-and-socket joints that are used in many different areas, but especially in the manufacture of vehicles, in assembly groups for the wheel suspension.
Such ball-and-socket joints comprise a joint housing which is open on at least one side with a housing recess and with a pivot pin, which is mounted in the housing recess with its joint ball provided with a surface protection, whose pin section protrudes from a housing opening. A bearing shell, which is necessary for the high loads on such joints in motor vehicles, is arranged between the joint housing and the joint ball.
It is very essential for the durable function of the ball-and-socket joint (long-term service life) to take design measures which make possible a permanent lubrication with joint grease. The friction between the components movable in relation to one another is considerably reduced as a result. A sealing bellows is used as the grease reservoir in conventional joints.
However, the sealing bellows is also indispensable for sealing the components of ball-and-socket joints for motor vehicles against contamination and environmental effects. The service life of a ball-and-socket joint may therefore be substantially reduced if, e.g., the sealing bellows is damaged and becomes leaky or is aged prematurely as a consequence of mechanical or thermal overstress or because of increased exposure to ozone, so that it no longer assumes its sealing function.
Another problem arises due to the fact that motor vehicles are often cleaned with high-pressure cleaning devices. It was possible to determine that these devices generate pressures that are able to lift off the sealing bellows from the components of the joint at least briefly and slightly. Leaks that develop as a result permit the entry of undesired media into the interior of the joint.
The technical object of the present invention is to achieve improved sealing of the ball-and-socket joint against the penetration of contaminants or moisture between the bearing shell and the joint ball while ensuring optimized lubrication function of the movable components of the joint at the same time.
The technical object is accomplished according to the present invention by a ball-and-socket joint with a joint housing which is open on at least one side, with a housing recess, with a pivot pin, which is mounted in the housing recess with its joint ball provided with surface protection, and whose pin section protrudes from the housing opening. A bearing shell is arranged between the joint housing and the joint ball. A closing ring closes the housing recess of the joint housing, tensions the bearing shell arranged therein in the joint housing, and essentially follows the outer contour of the bearing shell with its inner contour due to a bevel or a radius. It is proposed according to the present invention that the closing ring, which is to be inserted into the joint housing and is fixed on the side of the housing opening, through which the pin section of the pivot pin protrudes from the joint housing, be provided with a sealing lip which is in contact with the joint ball under elastic pretension.
It is essential for the practical embodiment of the present invention that the joint ball be provided with a surface protection, so that it has an extremely low roughness as well as a corrosion protection as a consequence of this treatment, because long service life of the sealing lip which is in sliding contact with the joint ball can be guaranteed by this only. The maximum surface roughness (Ry) should be approximately between 1 xcexcm and 5 xcexcm. 
The present invention offers a number of advantages. Thus, it would be possible to use two different types of grease within the ball-and-socket joint without mixing having to be feared. A first type of lubricating grease with optimal lubricating and sliding properties is provided between the joint ball and the bearing shell, with the sealing lip sealing the grease reservoir and holding it in this area of the joint. A second type of grease is accommodated in the sealing bellows and it assumes mainly a sealing function.
The additional sealing lip within the ball-and-socket joint thus guarantees not only an optimal lubrication of the joint, but at the same time also an optimal sealing function, which is of considerable advantage over prior-art designs especially in case of the use of high-pressure cleaning devices. A ball-and-socket joint according to the present invention could possibly even do entirely without a sealing bellows. At any rate, the efforts needed to achieve the firm seating of the sealing bellows can be reduced, however, so that it appears to be possible to make do without the use of tension rings, as a result of which not only the number of components present but also the efforts needed during the mounting of the ball-and-socket joints according to the present invention and consequently the costs can be reduced.
The closing ring may be designed in the manner of a flange on the side facing the pin section of the pivot pin and may have at least one bulge on its outer contour. By means of this the closing ring to be pressed into the joint housing is caused to engage the at least one recess of the inner surface of the joint housing in a fixed position.
According to another embodiment of a ball-and-socket joint according to the present invention, it is, furthermore, proposed that the sealing lip be made of rubber and that it be vulcanized to the closing ring, i.e., that a one-part component with the closing ring be manufactured or that it be inserted into a groove provided in the closing ring.
According to the present invention, the bulge on the outer contour of the closing ring may advantageously have a height of 0.2 mm to 0.3 mm in relation to the adjacent areas of its outer contour. This is already sufficient to achieve a significant increase in the pull-out strength due to this bulge engaging a corresponding recess of the joint housing over a depth corresponding to the height of the bulge, taking into account tolerances.
At the same time, a displacement of the bearing shell in the joint housing is prevented during the manufacturing process, especially during the at least partial material deformation, by which the flange-like section of the closing ring in the joint housing is determined and which may also be carried out by flanging the end areas of the joint housing. During the stressing of the joint during use, the solution according to the present invention guarantees secure fixation of the bearing shell against slipping, which could otherwise occur as a consequence of permissible wobbling movements of the pivot pin.
In a variant of the present invention, the bulge on the outer contour of the closing ring has the shape of a circular ring, which engages a circular groove provided on the inner surface of the joint housing. A plurality of circular ring-shaped bulges, which have, e.g., a sawtooth-like contour, may, of course, also be present.
If a plurality of circular ring-shaped bulges with a sawtooth-shaped contour are used, it may be advantageous to make a first flank of this sawtooth-shaped contour longer than each additional flank and to cause as a result the bulge extending with a slope in the direction of the housing opening to engage the groove, which has the same slope and extends circularly on the inner surface of the joint housing, in an interlocking manner. The firm seating of the closing ring in the joint housing is considerably improved as a result. To reduce the weight and to improve the elasticity of the components contacting one another, it is, furthermore, possible for the bulge extending circularly in the form of a ring on the outer contour of the closing ring to be interrupted in some areas or for the bearing shell to have a reduced wall thickness compared with the rest of its wall thickness in at least some sections in the area that is in contact with the inner contour of the closing ring.
To avoid the introduction of contaminants into the area between the bearing shell and the joint ball, it is, furthermore, advantageous to provide a smooth transition from the joint ball to the pivot section of the pivot pin, i.e., to keep the radius R of the transition between the joint ball and the pin section of the pivot pin at a minimum. There shall be no flute according to the present invention in this area.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.